A lens including a lens portion having two opposite oblong lens surfaces is known in the art. This lens may be formed by injecting or pouring into a mold a molten resin material which is then let cooled and solidified.
In order to smoothly remove a molded lens from a mold, two opposite oblong sides of the lens portion disposed adjacent to the longer sides of the oblong lens surfaces may be provided with flatly shaped draft surfaces which slant outwardly from one lens surface toward another at a predetermined angle. However, such a flatly shaped draft surface is formed with triangular prismatic portions added at those oblong sides of the lens portion, thus increasing the volume of the lens. The increase of the volume of the lens would require a longer period of time for injection, cooling, etc. during manufacture of the lens, and entail the disadvantages of increased manufacturing time.
There is a need to provide a lens with an advantage in shortened manufacturing time.